1. Technical Field
The present invention relates to a double dynamic focus electron gun for a cathode ray tube (CRT), and more particularly, to a double dynamic focus electron gun for a cathode ray tube in which a positive astigmatism correction is performed.
2. Related Art
In general, an electron gun for a color cathode ray tube installed at a neck portion of the cathode ray tube emits thermions. The performance thereof depends on the state of landing of an electron beam generated by the thermions onto a fluorescent film.
The electron gun is classified into a static focus electron gun and a dynamic focus electron gun. The dynamic focus electron gun reduces the occurrence of a phenomenon in which the shape of an electron beam emitted from an electron gun and landing on a fluorescent film becomes oval by being affected by a difference between a barrel magnetic field and a pincushion magnetic field as the electron beam is deflected by a deflection yoke. The dynamic focus electron gun makes the shape of the electron beam emitted from the electron gun relatively oval in synchronism with horizontal and vertical deflection periods. Recently, the dynamic focus electron gun is widely used.
U.S. Pat. No. 5,404,071, entitled DYNAMIC FOCUSING ELECTRON GUN, issued to Son on 4 Apr. 1995, relates to a dynamic focusing electron gun having more than two quadrupole lenses. In the case of arranging focusing lenses in increasing even numbers as in the technology of U.S. Pat. No. 5,404,071, the following problem occurs: as the current increases, the spherical aberration effect increases so that the horizontal resolution is deteriorated at the periphery of a screen.
As described above, the development of a dynamic focus electron gun concentrates on how much the resolution at the periphery of a screen can be improved. To reduce spherical aberration of the main lens in an electron gun disclosed in Japanese Patent Publication No. 3-95835, a main lens is formed asymmetrically and a focusing force in the horizontal direction is less than that of the vertical direction. However, when a large amount of current used, the effect of reducing the spherical aberration of the main lens is not sufficient.
Also, U.S. Pat. No. 5,744,917, entitled ELECTRON GUN ASSEMBLY FOR A COLOR CATHODE RAY TUBE APPARATUS, issued to Kawaharada on 28 Apr. 1998, relates to an electron gun with two quadruple lenses and a sub-lens. The gun of U.S. Pat. No. 5,744,917 needs additional installation of a separate electrode member which makes its manufacture complicated. Also a moirxc3xa9 effect at the periphery of the screen is not sufficiently prevented.
While the foregoing efforts provide advantages, we note that they fail to adequately provide a efficient, effective, and convenient double dynamic focus electron gun.
To solve the above-described problems, it is an object of the present invention to provide an electron gun for a cathode ray tube (CRT) in which a focus characteristic of an electron beam is improved so that a resolution at the periphery of a screen is improved.
To solve the above-described problems, it is a further object of the present invention to provide an electron gun for a cathode ray tube (CRT) in which a focus characteristic of an electron beam is uniform throughout the screen.
To solve the above-described problems, it is another object of the present invention to provide an electron gun for a cathode ray tube (CRT) in which a a horizontal resolution at the periphery of a screen is improved.
To achieve the above objects and others, there is provided an electron gun for a color cathode ray tube comprising a triode portion including a cathode emitting three electron beams and a control electrode and a screen electrode for controlling the electron beams and forming a cross-over point, an electron lens forming portion including first, second, third, fourth, and fifth focus electrodes and a final acceleration electrode, sequentially installed in a direction from the screen electrode to a fluorescent film of the cathode ray tube, for forming a plurality of electron lenses, and applying a voltage to form at least one auxiliary quadruple lens between the second and third focus electrodes, at least one first quadruple lens between the third and fourth focus electrodes, at least one second quadruple lens between the fourth and fifth focus electrodes, and at least one main lens between the fifth focus electrode and the final acceleration electrodes, by applying a screen voltage to the screen electrode and the second focus electrode, a static focus voltage to the first and fourth focus electrodes, a parabola type dynamic focus voltage synchronized with a deflection signal to the third and fifth focus electrodes, and an anode voltage to the final acceleration electrode.
It is preferred in the present invention that electron beam passing holes formed at the input side surface of the third focus electrode are vertically elongated in a direction in which the three electron beam passing holes are arranged, and that electron beam passing holes formed at the input side surface of the third focus electrode are formed by installing an electrode member having vertically elongated electron beam passing holes at the input side surface of the third focus electrode.
It is preferred in the present invention that the electron beams are vertically focused and horizontally diverged by the first quadruple lens, and vertically diverged and horizontally focused by the second quadruple lens, and that the electron beams are vertically diverged and horizontally focused by the auxiliary quadruple lens as the electron beams are deflected toward the periphery of a screen.
To achieve the above objects and others, there is provided an electron gun for a color cathode ray tube comprising a triode portion including a cathode emitting three electron beams and a control electrode and a screen electrode for controlling the electron beams and forming a cross-over point, an electron lens forming portion including first, second, third, fourth, and fifth focus electrodes and a final acceleration electrode, sequentially installed in a direction from the screen electrode to a fluorescent film of the cathode ray tube, for forming a plurality of electron lenses, and applying a voltage to form at least one auxiliary quadruple lens between the first and second focus electrodes, at least one first quadruple lens between the third and fourth focus electrodes, at least one second quadruple lens between the fourth and fifth focus electrodes, and at least one main lens between the fifth focus electrode and the final acceleration electrodes, by applying a screen voltage to the screen electrode, a static focus voltage to the first and fourth focus electrodes, a parabola type dynamic focus voltage synchronized with a deflection signal to second, third, and fifth focus electrodes, and an anode voltage to the final acceleration electrode.
It is preferred in the present invention that electron beam passing holes formed at the output side surface of the first focus electrode are horizontally elongated in a direction in which the three electron beam passing holes are arranged, and electron beam passing holes formed at the input side surface of the second focus electrode are vertically elongated in the direction in which the three electron beam passing holes are arranged.
It is preferred in the present invention that electron beam passing holes formed at the output side surface of the first focus electrode are formed by installing an electrode member having electron beam passing holes which are horizontally elongated in a direction in which the three electron beam passing holes are arranged, at the output side surface of the first focus electrode, and electron beam passing holes formed at the input side surface of the second focus electrode are formed by installing an electrode member having electron beam passing holes which are vertically elongated in the direction in which the three electron beam passing holes are arranged, at the input side surface of the second focus electrode.
It is preferred in the present invention that electron beam passing holes formed at the output side surface of the first focus electrode are vertically elongated in a direction in which the three electron beam passing holes are arranged, and electron beam passing holes formed at the input side surface of the second focus electrode have a circular shape or the shape of a keyhole having a circular central portion formed in a slot which is vertically elongated in a direction in which the three electron beam passing holes are arranged.
It is preferred in the present invention that electron beam passing holes formed at the output side surface of the first focus electrode are formed by installing an electrode member having electron beam passing holes which are vertically elongated in a direction in which the three electron beam passing holes are arranged, at the output side surface of the first focus electrode, and electron beam passing holes formed at the input side surface of the second focus electrode are formed by installing an electrode member having circular electron beam passing holes or electron beam passing holes having the shape of a keyhole having a circular central portion formed in a slot which is vertically elongated in a direction in which the three electron beam passing holes are arranged, at the input side surface of the second focus electrode.
It is preferred in the present invention that the electron beams are vertically focused and horizontally diverged by the first quadruple lens, and vertically diverged and horizontally focused by the second quadruple lens, and that the electron beams are vertically diverged and horizontally focused by the auxiliary quadruple lens as the electron beams are deflected toward the periphery of a screen.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an electron gun for a cathode ray tube, the electron gun comprising: a triode portion including at least one cathode emitting electron beams in a first direction toward a screen of a cathode ray tube, and including a control electrode and a screen electrode controlling the electron beams; a plurality of electrodes including first, second, third, fourth, and fifth focus electrodes and a final acceleration electrode sequentially installed in the first direction from the screen electrode to the screen, the plurality of electrodes forming a plurality of electron lenses; and applying a voltage to form at least one auxiliary quadruple lens between the second and third focus electrodes, forming at least one first quadruple lens between the third and fourth focus electrodes, forming at least one second quadruple lens between the fourth and fifth focus electrodes, and forming at least one main lens between the fifth focus electrode and the final acceleration electrode; the power supply performing the forming of the lenses by applying a screen voltage to the screen electrode and the second focus electrode, applying a static focus voltage to the first and fourth focus electrodes, applying a parabola type dynamic focus voltage synchronized with a deflection signal to the third and fifth focus electrodes, and applying an anode voltage to the final acceleration electrode.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an electron gun for a cathode ray tube, the electron gun comprising: a triode portion including at least one cathode emitting electron beams in a first direction toward a screen of a cathode ray tube, and including a control electrode and a screen electrode controlling the electron beams; a plurality of electrodes including first, second, third, fourth, and fifth focus electrodes and a final acceleration electrode sequentially installed in the first direction from the screen electrode to the screen, the plurality of electrodes forming a plurality of electron lenses; and applying a voltage to form at least one auxiliary quadruple lens between the first and second focus electrodes, forming at least one first quadruple lens between the third and fourth focus electrodes, forming at least one second quadruple lens between the fourth and fifth focus electrodes, and forming at least one main lens between the fifth focus electrode and the final acceleration electrode; the power supply performing the forming of the lenses by applying a screen voltage to the screen electrode, applying a static focus voltage to the first and fourth focus electrodes, applying a parabola type dynamic focus voltage synchronized with a deflection signal to the second, third, and fifth focus electrodes, and applying an anode voltage to the final acceleration electrode.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an electron gun for a cathode ray tube, the electron gun comprising: a triode portion including three cathodes emitting electron beams toward a screen of a cathode ray tube, and including a control electrode and a screen electrode controlling the electron beams, the three cathodes extending in a horizontal row; a plurality of electrodes including first, second, third, fourth, and fifth focus electrodes and a final acceleration electrode sequentially installed from the screen electrode to the screen, the plurality of electrodes forming a plurality of electron lenses; and applying a voltage to form at least one auxiliary quadruple lens between the second and third focus electrodes, forming at least one first quadruple lens between the third and fourth focus electrodes, forming at least one second quadruple lens between the fourth and fifth focus electrodes, and forming at least one main lens between the fifth focus electrode and the final acceleration electrode; the power supply performing the forming of the lenses by applying voltages to a selected subgroup of the electrodes, the selected subgroup being selected from among a first subgroup with the power supply applying a screen voltage to the screen electrode and the second focus electrode and applying a static focus voltage to the first and fourth focus electrodes and applying a parabola type dynamic focus voltage synchronized with a deflection signal to the third and fifth focus electrodes and applying an anode voltage to the final acceleration electrode, and a second subgroup with the power supply applying the screen voltage to the screen electrode, applying the static focus voltage to the first and fourth focus electrodes, applying the parabola type dynamic focus voltage synchronized with the deflection signal to the second, third, and fifth focus electrodes, and applying the anode voltage to the final acceleration electrode.
The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example. Other advantages and features will become apparent from the following description and from the claims.